In the past two decades, there has been a resurgence in union activity in the health care industry in the United States, particularly in hospitals. As health care unions become more influential in hospital operations, it is important that we better understand how unions affect health care and patient safety. This study has four specific objectives: (1) to measure the growth of hospital unions in the United States, using data at both the individual and hospital level, and to identify the factors that lead to hospital unionization; (2) to quantify the effects of hospital unions on wages, and to assess the effect of union-driven wage growth on growth in overall hospital costs; (3) to examine the relationship between unions and hospital nurse-to-patient ratios;and (4) to evaluate whether hospital unions improve patient safety and patient outcomes, both indirectly by improving working conditions and directly by improving process of care. This study will use national and state data to address the objectives, with a focus on eleven states from 1990 through 2006. The primary patient outcomes used in this study will be derived from the AHRQ Patient Safety Indicators and Inpatient Quality Indicators. The datasets to be used in this study include a dataset on unionization in hospitals to be developed in this project, the AHRQ Nationwide Inpatient Sample, the American Hospital Association Annual Survey of Hospitals, the California Office of Statewide Health Planning and Development patient and hospital data, and the US Bureau of the Census Current Population Survey. The analytical strategy used throughout this study is that of multivariate regression analysis. The research team will use econometric methods that control for differences between hospitals and the possibility that different hospital characteristics cause unionization, rather than result from unionization. This project will improve our understanding of how hospitals deliver safe, effective care to patients. Previous research has found that unionized hospitals have lower heart attack mortality rates, but at this time we do not understand why this relationship exists. This study will delve into the "black box" of hospital unionization to learn whether and how unions affect the delivery and quality of care.